Spring suspension arrangements as mentioned above are suitable for, for instance, a flat bed vehicle onto and off which a load unit is loaded or off-loaded, a typical load unit being perhaps a dwelling unit such as a camper body. In these vehicles, the loading by the load unit generally is very great in proportion to the actual weight of the vehicle, and by the mentioned increase of the bearing force, the springing of the vehicle when the load unit is set on it is reduced, and the spring properties can be favorably influenced for comfortable springing.
In a spring suspension arrangement of this type, known from German OS No. 20 04 510, a self-pumping and level-regulating spring element has a high pressure chamber and a low pressure chamber, whereby in the down-adjusted state the same pressure prevails in both chambers, and a bearing load or force, the "basic load or force" associated with the empty state of the vehicle, is determined by the pressure of the low pressure chamber, whereby to increase the basic load, pressure media are supplied by pumping devices, from a shunt chamber into the low pressure chamber. In this German document, it is indicated that the shunt chamber can be provided by a cylinder with a piston that can be moved back and forth by means of a screw pin. Such actuation of a piston is disadvantageously cumbersome.
The instant invention is concerned with the problem of effecting the forwarding of pressure medium from a shunt chamber or the like by simple means, in a spring suspension of the above mentioned type, and the invention accordingly includes spring suspensions with a high pressure chamber and a low pressure chamber as in the German document, and also those that have a high pressure chamber exclusively. The problem is solved in that the shunt chamber or pressure source comprises an auxiliary cylinder connected with the load bed, with an auxiliary piston provided with receiving or holding devices for a load unit, such that the piston is automatically thrust from an extended state to a retracted state when the load unit is set on, resulting in the delivery of pressure medium from the shunt chamber to the spring suspension elements.
In accordance with the invention, advantageously the weight of the load unit is used to effect delivery of pressure medium from the shunt chamber, i.e., the auxiliary cylinder, into the spring suspension element, and for this no special actuating means are required. Preferably the retracted position of the auxiliary piston is limited by engagement of the load unit onto the load bed, such that when the load unit rests on the load bed, the auxiliary piston is in its fully retracted position. In off-loading the load unit, the pressure medium flows back into the auxiliary cylinder under the effect of the gas cushion in the spring element, and the auxiliary piston is again thrust into its extended position. In this way, the spring suspension element and the auxiliary cylinder influence each other.
The hydropneumatic spring suspension device according to the invention can be made fully bearing or partly bearing together with another spring suspension device for one or more axles. If the load bed essentially is borne by an axle equipped with two spring suspension elements, then in the simplest case each spring element is connected with an auxiliary cylinder. Groups of spring elements and auxiliary cylinders for one or more axles are also possible, which mutually influence each other, and may be connected with one auxiliary cylinder for one or more spring elements, or vice versa.
Other features, objects and advantages of the invention will be apparent to those skilled in the art from the ensuing description of preferred embodiments, taken in conjunction with the appended drawings.